Venturi induction for heat recovery and low nox internal combustion engines

ABSTRACT

Internal combustion engine heat is recovered by charge air for useful work and to increase engine thermal efficiency. A dual liquid/air cooling system is presented to facilitate heat recovery. Water is injected into a pintle-regulated Venturi to mitigate the engine charge temperature, control the combustion temperature and reduce NOx emissions.

SUMMARY OF THE INVENTION

This invention improves the thermodynamic efficiency while reducing NOx emission of internal combustion engines. A simplistic approach is to homogeneously mix water with fuel and air in a pintle-regulated Venturi to reduce the combustion temperature. A second approach is described to increase engine efficiency, whereby exhaust heat is recovered by incoming air and subsequently cooled by water injection in a Venturi. A third approach recovers heat from the combustion chamber and exhaust, increasing the heat recovery potential. Fuel could be gasoline but could also be natural gas, other hydrocarbons, alcohols, or diesel.

BACKGROUND OF THE INVENTION

In a conventional internal combustion engine, coolant heat rejection ranges from 10-35% of the combustion energy. Exhaust heat loss is usually 20-45% of the combustion energy. Consequently, there is substantial room for improving the thermodynamic efficiency of the internal combustion engine.

Air is composed of 78 volume percent nitrogen. Nitrogen oxidizes when fuel is burned at high temperatures, as in a combustion process to form nitrogen oxides. Nitrogen oxides consist of a group of oxidized nitrogen compounds collectively known as NOx. Many of the nitrogen oxides are colorless and odorless. However, one common pollutant, nitrogen dioxide (NO₂) along with particles in the air can often be seen as a reddish-brown layer over many urban areas. The primary source of NOx is motor vehicles. Production of NOx increases with the time and temperature of combustion.

NOx is generated exponentially with increasing flame temperature and decreases exponentially with water injection in the flame zone. NOx emissions can therefore be reduced by eliminating nitrogen from the intake vapor mixture and/or reducing the combustion temperature by saturating the intake vapor mixture with water.

Of the six pollutants (carbon monoxide, lead, nitrogen oxides, particulate matter, sulfur dioxide, and volatile organic compounds) tracked by the Environmental Protection Agency, all have decreased significantly since passage of the Clean Air Act in 1970—except for nitrogen oxides

The differential producing Venturi has a long history of uses in many applications. With no abrupt flow restrictions, the Venturi can mix gases and liquids with a minimal total pressure loss. Recently, the Venturi has been used in carbureted engines. The suction from the throat of the Venturi provided the motive force for bringing the fuel in contact with the air. The improved application of the Venturi with the proposed invention is: the metering of the fuel is controlled by the fuel injector instead of the suction of the venturi; the fuel vaporization is facilitated by the reduced pressure in the throat of the Venturi; and mixing of the fuel/vapor mixture is enhanced by the turbulent action in the outlet of the Venturi.

The principle behind the operation of the Venturi is the Bernoulli effect. The Venturi mixes vapors and liquids by reducing the cross sectional flow area in the vapor flow path, resulting in a pressure reduction in the throat of the Venturi. After the pressure reduction, the mixture is passed through a pressure recovery exit section where most of the pressure reduction is recovered. The pressure differential follows Bernoulli's Equation, simplified for a negligible change in elevation: P ₁+½d ₁ v ₁ ² =P ₂+½d ₂ v ₂ ²

where,

P₁=Pressure at the inlet of Venturi (FIG. 1, location 101);

P₂=Pressure at the throat of the Venturi (FIG. 1, location 102);

d₁=vapor density at the inlet of the Venturi (FIG. 1, location 101);

d₂=vapor density at the throat of the Venturi (FIG. 1, location 102);

v₁=vapor velocity at the inlet of the Venturi (FIG. 1, location 101) and;

v₂=vapor velocity at the throat of the Venturi (FIG. 1, location 102).

In FIG. 1, the vapor enters the Venturi at the location 101 with a cross-sectional area A₁, pressure P₁, and velocity v₁. These properties form the potential and kinetic energy of the fluid at one location. Energy is conserved in a closed system, that is, the sum of potential and kinetic energy at one location must equal the sum of the potential and kinetic energy at any another location in the system. If potential energy decreases at one location, the kinetic energy must proportionally increase at that location. The fluid enters the throat of the Venturi at location 102 with a new area A₂, which is smaller than A₁. In a closed system mass can be neither created nor destroyed (law of conservation of mass), and as such, the volumetric flow rate at area A₁ must equal the volumetric flow rate at area A₂. If the area at location A₂ is smaller than A₁, the fluid must travel faster to maintain the same volumetric flow rate. This increase in velocity results in a decrease in pressure according to the Bernoulli's equation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow diagram for a typical Venturi.

FIG. 2 is a diagram of a fuel/vapor intake passage improved by an unregulated Venturi.

FIG. 3 is a diagram of a fuel/vapor/water delivery system using a pintle-regulated Venturi to deliver a homogeneous vapor, fuel and air charge to a liquid-cooled internal combustion engine.

FIG. 4 is a diagram of a fuel/vapor/water delivery system using a pintle-regulated Venturi to deliver a homogeneous vapor, fuel and air charge to an internal combustion engine with dual chamber liquid/vapor cooling

FIG. 5 is a process flow diagram of an internal combustion engine system using ambient air and water injection to control production of NOx.

FIG. 6 is a process flow diagram of an internal combustion engine system using exhaust-heated ambient air to improve thermodynamic efficiency and water injection to control production of NOx.

FIG. 7 is a process flow diagram of an internal combustion engine system using exhaust-heated turbocharged air to improve thermodynamic efficiency with an intercooler and water injection to control production of NOx.

FIG. 8 is a process flow diagram of an engine system recovering heat from both the exhaust and combustion chamber. Supercharged heated air improves thermodynamic efficiency while an intercooler and water injector controls production of NOx.

DETAILED DESCRIPTION

Three methods are presented for reducing NOx in an internal combustion engine. Air is defined for the purposes of this disclosure as a vapor containing oxygen. Water is defined as liquid containing water, recognizing that anti-freeze components may be required for cold weather operation.

In the first method, water is injected into the throat of the Venturi where homogeneous mixing is accomplished with fuel and air. NOx emission is reduced because of the resulting lower combustion temperature due to water injection.

The second method utilizes engine exhaust to heat charge air. The heated air is cooled by water injected into a Venturi passing the heated air charge. The thermal efficiency of the engine is improved without overheating the engine because heat is absorbed by the injected water. Specifically, engine overheating is prevented by 1) the low water temperature relative to the air charge and 2) the latent heat of evaporation of the water in the Venturi. Exhaust heat is therefore recovered by the water liquid-to-vapor phase change between the point of injection and combustion outlet valve.

The third method recovers heat from the engine exhaust and the combustion chamber. Charge air, compressed by a supercharger or turbocharger is heated by the exhaust and the combustion chamber. Recognizing that the combustion chamber temperature must be regulated, a dual chamber is depicted whereby the inner liquid coolant is temperature controlled as in a conventional engine. However, heat is also conveyed to the outer chamber where combustion heat is transferred to charge air. Heat transfer to the outer air chamber can be facilitated by fins projecting through the inner and outer chamber partition.

The heated charge air is controlled by an ambient air-cooled inter-cooler to ensure the charge air never becomes overheated beyond the capability of the water injection to control the combustion temperature. Otherwise, the combustion temperature inside the cylinder could potentially become too hot for conventional engine materials. The control strategy will maximize heat recovery by water injection to optimize engine efficiency.

With the pintle-regulated Venturi design, the fuel becomes well mixed with the vapor because: 1) the pressure reduction at the Venturi throat increases the partial pressure of the fuel, promoting fuel vaporization and; 2) turbulence through the Venturi facilitates fuel/vapor mixing before the combustion chamber. The pintle-regulated Venturi design enhances fuel/vapor mixing at all throttle vapor rates by combining vapor flow control with the Venturi design. The resulting flow area reduction provides a higher velocity at low throttle than an unregulated Venturi design. For example, when a car is cruising down the highway at low throttle, the pintle is relatively closed into the throat of the Venturi. Consequently, mixing velocity is much higher and mixing is more complete across the entire throttle range relative to an unregulated Venturi or a common butterfly valve intake system.

The water injection rate for all three methods is controlled by the exhaust temperature sensor.

FIG. 2 illustrates an internal combustion engine intake system with an unregulated Venturi delivery system. Vapor 201 flows into the Venturi either from natural engine suction or pressurized flow from a supercharger or a turbocharger. The vapor flows into the Venturi throat 202 where the pressure is reduced according to the Bernoulli equation. Fuel is metered into the throat of the Venturi with a fuel injector 203. The mixed fuel/vapor mixture leaves the Venturi and enters the combustion chamber through the intake valve 204

FIG. 3 illustrates a regulated fuel/vapor delivery system for a liquid-cooled engine using a Venturi and integrated pintle throttle design. Vapor 301 flows into the Venturi either from engine suction, or pressurization from a supercharger or turbocharger. The vapor rate is regulated by a pintle throttle 305. The throttle position is modulated by an actuator 307 and moves 306 as required by the engine controls. The vapor flows into the Venturi throat 308 where the pressure is reduced according to the Bernoulli equation. Fuel is metered into the throat of the Venturi with a fuel injector 302. The fuel can be introduced from a fixed location as indicated in FIG. 3 or introduced through the pintle throttle 305. The mixed fuel/vapor mixture leaves the Venturi and enters the combustion chamber through the intake valve 309. Water is injected into the combustion chamber via the Venturi through injector 303 and the pintle openings 304 as required by the engine controls. Although FIG. 3 shows a water injector upstream of the pintle, the water injector could be positioned inside the pintle to facilitate dispersion of water into a Venturi. Exhaust exits the combustion chamber through exhaust valve 310 and leaves the engine through the manifold 314. The liquid-cooled engine design is depicted with cooling chamber 311, coolant inlet 312 and coolant outlet 313.

FIG. 4 illustrates a regulated fuel/vapor delivery system for a dual cooling chamber engine using a Venturi and integrated pintle throttle design. Vapor 401 flows into the Venturi either from engine suction, or pressurization from a supercharger or turbocharger. The vapor rate is regulated by a pintle throttle 405. The throttle position is modulated by an actuator 407 and moves 406 as required by the engine controls. The vapor flows into the Venturi throat 408 where the pressure is reduced according to the Bernoulli equation. Fuel is metered into the throat of the Venturi with a fuel injector 402. The fuel can be introduced from a fixed location as indicated in FIG. 3 or introduced through the pintle throttle 405. The mixed fuel/vapor mixture leaves the Venturi and enters the combustion chamber through the intake valve 409. Water is injected into the combustion chamber via the Venturi through injector 403 and the pintle openings 404 as required by the engine controls. Although FIG. 4 shows a water injector upstream of the pintle, the water injector could be positioned inside the pintle to facilitate dispersion of water into a Venturi. Exhaust exits the combustion chamber through exhaust valve 410 and leaves the engine through the manifold 411. The dual cooling chamber consist of an inner chamber 414 and an outer chamber 416 separated by a partition 418. Liquid coolant enters the inner chamber via port 414 and exits the inner chamber via port 412. Air coolant enters the outer chamber via port 417 and exits the outer chamber via port 415.

FIG. 5 illustrates a pintle-regulated Venturi for an engine using ambient air. Charge air 502 flows towards a Venturi where fuel 503 and water 501 mix. The air, fuel and water become well-mixed at all throttle settings 507 because of the high velocity characteristic of a pintle-regulated Venturi. The charge water rate 501 is regulated by the engine controls 505 and the exhaust 504 temperature transmitter 506. The lower combustion temperature from water injection reduces NOx emission.

FIG. 6 depicts charge air 601 heated by exhaust 602 using a double-wall exhaust pipe 603. Air heat is retained by passing the heated charge air through an evacuated double-wall pipe or insulated pipe 604 to a Venturi. The fuel rate 605 through the fuel injector 607 is controlled by the exhaust analytical sensor 608 and the analytical sensor control 609 in the engine computer. The air rate is controlled by the throttle 610. Air and fuel is homogeneously mixed in the Venturi and cooled by water injection 606. The exhaust temperature sensor 613 sends a control signal to the exhaust temperature control in the computer 611. The water injection rate is then regulated by the engine computer 611 to control the combustion temperature and reduce NOx emissions.

FIG. 7 depicts a turbocharger 713 to overcome frictional losses in the air delivery system. Although a turbocharger is depicted, a supercharger would have a similar effect. The additional pressure from the turbocharger facilitates mixing in the Venturi. Charge air 701 is heated by exhaust 702 using a double-wall exhaust pipe 703. The heat of the air is retained by passing the heated charge air through an evacuated double-wall pipe or insulated pipe 704. The heated charge air is tempered if necessary by an intercooler 715 to ensure the charge air never becomes overheated beyond the capability of the water injection to control the combustion temperature. The fuel rate 705 through the fuel injector 707 is controlled by the exhaust analytical sensor 708 and the analytical sensor control 709 in the engine computer. The air rate is controlled by the throttle 710. Air and fuel is homogeneously mixed in the Venturi and cooled by water injection 706. The exhaust temperature sensor 714 sends a control signal to the exhaust temperature control in the computer 711. The water injection rate is then regulated by the engine computer 711 to control the combustion temperature reduce NOx emissions.

FIG. 8 depicts a supercharger 802 to overcome frictional losses in the air delivery system. Although a supercharger is depicted, a turbocharger would have a similar effect. Charge air 801 is heated by the exhaust 810 using a double-wall exhaust pipe or low pressure loss heat exchanger 804 and the outer engine coolant chamber. The heat of the air is retained by passing the heated charge air through an evacuated double-wall or insulated pipe 806. The heated charge air is tempered if necessary by an intercooler 807 to ensure the charge air never becomes overheated beyond the capability of the water injection to control the combustion temperature. The additional pressure from the supercharger facilitates mixing in the Venturi. The fuel rate 813 through the fuel injector 814 is controlled by the exhaust analytical sensor 811 and the analytical sensor control 812 in the engine computer. The air rate is controlled by the throttle 809. Air and fuel is homogeneously mixed in the Venturi and cooled by water injection 817. The exhaust temperature sensor 815 sends a control signal to the exhaust temperature control in the computer 816. The water injection rate 817 is then regulated by the engine computer 816 to control the combustion temperature reduce NOx emissions. Liquid coolant 818 flows into the inner combustion cooling chamber, regulated by a typical engine thermostat, and exits the inner cooling chamber via port 819.

The thermal efficiency of the engine is improved by heat recovery from the combustion products to the charge air. NOx emissions are controlled and reduced by regulating the combustion temperature with water injection. 

1. A double-wall exhaust pipe carrying exhaust inside a center pipe heats charge air flowing through an annulus, whereby heated charge air as stated in claim 5 is provided to a spark-ignition or compression ignition engine.
 2. A double-wall pipe conveys heated charge air in the center channel and an evacuated annulus minimizes heat loss, whereby heated charge air as stated in claim 5 is provided to a spark ignition or compression ignition engine.
 3. A dual medium coolant system comprised of an inner chamber for liquid cooling and an outer chamber for air cooling; the liquid-cooled chamber controls the engine temperature with a flow control thermostat; charge air is conveyed through the outer chamber to the engine for combustion; whereby heated charge air as stated in claim 5 is provided to a spark ignition or compression ignition engine.
 4. A dual coolant chamber comprised of an inner chamber for liquid cooling and an outer chamber for air cooling, with fins spanning from the inner liquid-cooled chamber to the outer vapor-cooled chamber to increase heat transfer to the outer air-cooled heat transfer chamber; the liquid-cooled chamber controls the engine temperature with a flow control thermostat; charge air is conveyed through the outer chamber to the engine for combustion: whereby heated charge air as stated in claim 5 is provided to a spark ignition or compression ignition engine.
 5. Heated charge air and water is injected into a pintle-regulated Venturi; whereby the engine combustion temperature is controlled by the water injection rate in a spark ignition or compression ignition engine. 